Journal of Powder Materials

Magnetic Properties and Sintering Behavior of (Nd,Dy)-Fe-B Permanent Magnet by Spark Plasma Sintering: Sun-Yong Song, Jin-Woo Kim, Se-Hoon Kim, Young-Do Kim; J Korean Powder Metall Inst. 2012;19(2):105-109.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.105

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Magnetic properties and the microstructures of magnets prepared by spark plasma sintering were investigated in order to enhance magnetic properties by grain size control. Nd-Fe-B magnets were fabricated by the spark plasma sintering under 30 MPa at various temperatures. The grain size was effectively controlled by the spark plasma sintering and it was possible to make Nd-Fe-B magnets with grain size of 5.9 µm.

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Development of Fe-Mn-based Hybrid Materials Containing Nano-scale Oxides by a Powder Metallurgical Route
Jonggyu Jeon, Jungjoon Kim, Hyunjoo Choi
Journal of Korean Powder Metallurgy Institute.2020; 27(3): 203. CrossRef

Effect of Heat Treatment Environment on the Densification of Cold Sprayed Ti Coating Layer: Ji-Sang Yu, Hyung-Jun Kim, Ik-Hyun Oh, Kee-Ahn Lee; J Korean Powder Metall Inst. 2012;19(2):110-116.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.110

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This study investigated the effects of annealing environment for the densification and purification properties of pure titanium coating layer manufactured by cold spraying. The annealing was conducted at 600°C/1 h and three kinds of environments of vacuum, Ar gas, and 5%H_2+Ar mixture gas were controlled. Cold sprayed Ti coating layer (as sprayed) represented 6.7% of porosity and 228 HV of hardness, showing elongated particle shapes (severe plastic deformation) perpendicular to injection direction. Regardless of gas environments, all thermally heat treated coating layers consisted of pure alpha-Ti and minimal oxide. Vacuum environment during heat treatment represented superior densification properties (3.8% porosity, 156.7 HV) to those of Ar gas (5.3%, 144.5 HV) and 5%H_2+Ar mixture gas (5.5%, 153.1 HV). From the results of phase analysis (XRD, EPMA, SEM, EDS), it was found that the vacuum environment during heat treatment could be effective for reducing oxide contents (purification) in the Ti coating layer. The characteristic of microstructural evolution with heat treatment was found to be different at three different gas environments. The controlling method for improving densification and purification in the cold sprayed Ti coating material was also discussed.

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Effect of Hot Isostatic Pressing on the Microstructure and Propertiesof Kinetic Sprayed Nb Coating Material
Ji-Hye Lee, Sangsun Yang, Kee-Ahn Lee
Journal of Korean Powder Metallurgy Institute.2016; 23(1): 15. CrossRef
Fabrication and Microstructure/Properties of Bulk-typeTantalum Material by a Kinetic Spray Process
Ji-Hye Lee, Ji-Won Kim, Kee-Ahn Lee
Journal of Korean Powder Metallurgy Institute.2016; 23(1): 8. CrossRef
Effect of Heat Treatment Environment on the Microstructure and Properties of Kinetic Sprayed Tantalum Coating Layer
Ji-Hye Lee, Hyung-Jun Kim, Kee-Ahn Lee
Journal of Korean Powder Metallurgy Institute.2015; 22(1): 32. CrossRef
Effect of Powder Preheating Temperature on the Properties of Titanium Coating Layers Manufactured by Kinetic Spraying
Kee-Ahn Lee, Myeong-Ju Lee, Ji-Sang Yu, Hyung-Jun Kim
MATERIALS TRANSACTIONS.2014; 55(3): 622. CrossRef
Effect of Carrier Gases on the Microstructure and Properties of Ti Coating Layers Manufactured by Cold Spraying
Myeong-Ju Lee, Hyung-Jun Kim, Ik-Hyun Oh, Kee-Ahn Lee
Journal of Korean Powder Metallurgy Institute.2013; 20(1): 24. CrossRef
Effects of Powder Morphology and Powder Preheating on the Properties and Deposition Behavior of Titanium Coating Layer Manufactured by Cold Spraying
Jae-Nam Hwang, Myeong-Ju Lee, Hyung-Jun Kim, Ik-Hyun Oh, Kee-Ahn Lee
Journal of Korean Powder Metallurgy Institute.2012; 19(5): 348. CrossRef

A Study on the Sintering Behavior of T42 High Speed Steel by Powder Injection Molding (PIM) Process: Dong-Wook Park, Hye-Seong Kim, Young-Sam Kwon, Kwon-Koo Cho, Su-Gun Lim, In-Shup Ahn; J Korean Powder Metall Inst. 2012;19(2):117-121.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.117

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Tool steels serve a large range of applications including hot and cold workings of metals and injection mouldings of plastics or light alloys. The high speed steels (HSS) are specifically used as cutting tools and wear parts because it has high strength, wear resistance and hardness along with appreciable toughness and fatigue resistance. From the view of HSS microstructure, it can be described as metallic matrix composites formed by a ferrous with a dispersion of hard and wear resistant carbides. The experimental specimens were manufactured using the PIM with T42 powders (50~80 vol.%) and polymer (20~50 vol.%). The green parts were debinded in n-hexane solution at 60°C for 8 hours and thermal debinded at an N_2-H_2 mixed gas atmosphere for 8 hours. Specimens were sintered in high vacuum (10-5 Torr) and various temperatures.

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Effects Of Process Parameters On Cu Powder Synthesis Yield And Particle Size In A Wet-Chemical Process
Y.M. Shin, J.-H. Lee
Archives of Metallurgy and Materials.2015; 60(2): 1247. CrossRef

Microstructure and Hardness of TiC Particle-reinforced Fe Self-fluxing Alloy Powders Based Hybrid Composite Prepared by High Energy Ball Milling: Sung-Jin Park, Yo-Seung Song, Ki-Seok Nam, Si-Young Chang; J Korean Powder Metall Inst. 2012;19(2):122-126.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.122

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The Fe-based self-fluxing alloy powders and TiC particles were ball-milled and subsequently compacted and sintered at various temperatures, resulting in the TiC particle-reinforced Fe self-fluxing alloy hybrid composite, and the microstructure and micro-hardness were investigated. The initial Fe-based self-fluxing alloy powders and TiC particles showed the spherical shape with a mean size of approximately 80 µm and the irregular shape of less than 5 µm, respectively. After ball-milling at 800 rpm for 5 h, the powder mixture of Fe-based self-fluxing alloy powders and TiC particles formed into the agglomerated powders with the size of approximately 10 µm that was composed of the nanosized TiC particles and nano-sized alloy particles. The TiC particle-reinforced Fe-based self-fluxing alloy hybrid composite sintered at 1173 K revealed a much denser microstructure and higher micro-hardness than that sintered at 1073 K and 1273 K.

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Compaction and Sintering Characteristics of High Energy Ball Milled Mn-Zn Ferrite Powders
Hyunseung Lee, Hoseong Rhee, Sangsoo Lee, Si Young Chang
Korean Journal of Materials Research.2021; 31(12): 677. CrossRef

Behaviors and Process Analyses of Spark Sintering for Powders Having a Low Sinterability: K. Matsugi; J Korean Powder Metall Inst. 2012;19(2):127-133.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.127

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The sintering behaviors and process parameters of some compounds (carbides, oxides, sulfides, borides) were investigated experimentally. These compounds were successfully consolidated and showed high densities. Some unique phenomena such as retardation of grain growth, suppression of thermal decomposition and maintenance of initial non-equilibrium phases, were observed by the proper control of process in spark sintering.

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Spark Sintering of TiB₂ Reinforced Fe Matrix Composites with Both High Thermal Conductivity and Hardness, and Their Microstructural Characterizations
Yujiao Ke, Kazuhiro Matsugi, Zhefeng Xu, Yongbum Choi, Mingzhi Wang, Jinku Yu
MATERIALS TRANSACTIONS.2020; 61(3): 548. CrossRef
Synthesis of 30 vol%TiB₂ Containing Fe–5Ti Matrix Composites with High Thermal Conductivity and Hardness
Yujiao Ke, Kazuhiro Matsugi, Zhefeng Xu, Yu He, Yongbum Choi, Mingzhi Wang, Jinku Yu
MATERIALS TRANSACTIONS.2019; 60(12): 2516. CrossRef
Process Analyses and Control in Spark Sintering for Powders having a Low Sinterability
Kazuhiro Matsugi, Kensho Tomigahara, Zhefeng Xu, Yongbum Choi, Gen Sasaki
Journal of the Japan Society of Powder and Powder Metallurgy.2012; 59(9): 525. CrossRef

Microstructural Evolution during Hot Deformation of P/M Copper using Processing Map: Soo-Ho Chang, Young-Moo Kim, Kyung-Chae Park; J Korean Powder Metall Inst. 2012;19(2):134-139.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.134

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P/M coppers are subjected to the isothermal compression tests at the strain rate ranging from 0.01 to 10.0 s-1 and the temperature from 200 to 800°C. The processing map reveals the dynamic recrystallization (DRX) domain in the following temperature and strain rate ranges: 600-800°C and 0.01-10.0 s-1, respectively. In the domain, the region at temperature of 600°C and strain rate of 10-2s-1 shows peak efficiency. From the kinetic analysis, the apparent activation energy in the DRX domain is 190.67 kJ/mol and it suggests that lattice self-diffusion is the rate controlling mechanism.

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High Temperature Deformation and Microstructural Evolution of Homogenized AA 2026 Alloy
HyeonWoo Kang, SooBin Kim, ByoungLok Jang, HeeKook Kim
Korean Journal of Metals and Materials.2023; 61(5): 338. CrossRef
Hot Deformation Behavior and Microstructural Evolution of Powder Metallurgy Ti-6Al-4V Alloy
Youngmoo Kim, Young-Beom Song, Sung Ho Lee, Young-Sam Kwon
Journal of Korean Powder Metallurgy Institute.2014; 21(4): 277. CrossRef

Manufacturing of Micro Gas Bearing by Fe-Ni Nanopowder and Metal Mold Using LIGA: Soo-Jung Son, Young-Sang Cho, Dae-Jung Kim, Jong-Hyun Kim, Suk-Sang Chang, Chul-Jin Choi; J Korean Powder Metall Inst. 2012;19(2):140-145.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.140

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This paper describes the manufacturing process of tilting pad gas bearing with a diameter of 5 mm and a length of 0.5-1 mm for power MEMS (Micro Electomechanical Systems) applications. The bearing compacts with nanopowder feedstock were prepared by Ni-metal mold with 2-mold system using LIGA process. The effect of the manufacturing conditions on sintering properties of nanopowder gas bearing was investigated. In this work, Fe-45 wt%Ni nanopowder with an average diameter of 30-50 nm size was used as starting material. After mixing the nanopowder and the wax-based binders, the amount of powder was controlled to obtain the certain mixing ratio. The nanopowder bearing compacts were sintered with 1-2 hr holding time under hydrogen atmospheres and under temperatures of 600°C to 1,000°C. Finally, the critical batch of mixed powder system was found to be 70% particle fraction in total volume. The maximum density of the sintered bearing specimen was about 94% of theoretical density.

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A comprehensive review on advancements in compliant structures of gas foil journal bearings
Srusti Priyadarshini, Suraj K Behera
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology.2024;[Epub] CrossRef

Effects of Nano Fe_xC Addition on Superconducting Properties of MgB₂: Dong-Gun Lee, Ji-Hyun Lee, Byung-Hyuk Jun, Soon-Dong Park, Young-Rang Uhm, Hai-Woong Park, Chan-Joong Kim; J Korean Powder Metall Inst. 2012;19(2):146-150.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.146

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Abstract PDF: The effects of nano Fe_xC addition to superconducting properties of in situ processed MgB_2 superconductors was examined. 0.1 wt.% and 1 wt.% nano Fe_xC powders were mixed with boron and magnesium powders by ball milling. The powder mixtures were made into pellets by uniaxial pressing. The pellets were heat-treated at 700°C-900°C in argon atmosphere for MgB_2 formation. It was found by powder X-ray diffraction that the raw powders were completely converted into MgB_2 after the heat treatment. The superconducting transition temperature (T_c) and critical current density (J_c), estimated from susceptibility-temperature and M-H curves, were decreased by nano Fe_xC addition. The T_c and J_c decrease by nano Fe_xC addition are attributed to the incorporation of iron and carbon with MgB_2 lattices (Fe substitution for Mg and C substitution for B) due to the high reactivity of the nano Fe_xC powder.

Trend in Research and Development Related to Lean Heavy Rare-earth Permanent Magnets for Next-generation Motors: Jung-Goo Lee, Youn-Kyoung Baek, Ji-Hun Yu, Chul-Jin Choi; J Korean Powder Metall Inst. 2012;19(2):151-159.; DOI: https://doi.org/10.4150/KPMI.2012.19.2.151

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Study on the Demagnetization and Classification of NdFeB Magnets According to Different Heat Treatment Temperatures
Byeong Jun Kim, Ik Keun Park, Young Sung Kim
Journal of the Korean Society of Manufacturing Technology Engineers.2021; 30(2): 119. CrossRef
Low Cost Design Study of Brushless DC Motor for Electric Water Pump Application
Tae-Uk Jung
Journal of Electrical Engineering and Technology.2014; 9(3): 942. CrossRef
Optimized Design of Rotor Considering Cost-Reduction of Small BLDC Motor for the Water Pump
Hoe-Cheon Kim, Tae-Uk Jung
The Transactions of The Korean Institute of Electrical Engineers.2013; 62(4): 495. CrossRef

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